Is there any bona fide example of O–H⋯F–C bond in solution? The cases of HOC(CF3)2(4-X-2,6-C6H2(CF3)2) (X = Si(i-Pr)3, CF3)

Abstract

The reinvestigation of the title compounds, which are the only examples reported to show experimentally (by NMR) O-H...F-C bonds in solution proves that the NMR data were misinterpreted and the restrictions to rotation of one CF(3) group are due to crowding, not to intramolecular O-H...F-C bond.

Organic fluorine involved intramolecular hydrogen bonds in the derivatives of imides: NMR evidence corroborated by DFT based theoretical calculations

“…This change in chemical shift arises due to the variation in the concentration, alteration in the polarity of the solvent, and the temperature alteration. In order to distinguish the intra-and inter-molecular HB and to monitor the effect of atmospheric monomeric water on HB, the solvent titration experiments [34][35][36]72 were performed on the molecules 1-7 in the solvent CDCl 3 . The plot of variation of the chemical shift as a function of solvent concentration is reported in High polarity solvent dimethyl sulphoxide (DMSO) is a very good HB acceptor and hence it can rupture the variety of inter-and intra-molecular HBs 44,45 .…”

“…Furthermore it is well known that nearly 30% of the commercially available drug molecules contain at least one fluorine atom. In addition, the organofluorine molecules have enormous importance due to their applicability as biomaterials, agro chemicals, in molecular imaging, 23,24 crystal engineering [25][26][27] and also in the functional materials designing 28 [34][35][36] . The nuclear magnetic resonance (NMR) and X-ray crystallographic studies have been reported on the N-H … F-C HB in foldamers and benzanilides 37,38 .…”

Intramolecular hydrogen bonds involving organic fluorine in the derivatives of hydrazides: an NMR investigation substantiated by DFT based theoretical calculations

“…In bio-inorganic and medicinal chemistry, the formation of intermolecular X-H … F-C (X=O, N) hydrogen bridges is significantly important because of the binding nature of the fluorinated compounds to enzyme active sites. However, there are very few reports of the involvement of organic fluorine in the HB in the solution state [50][51][52] . This is also substantiated by a report of Dunitz and co-workers entitled ''organic fluorine hardly ever accepts hydrogen bonds'' [46][47][48][49] .…”

Synthesis, variable temperature NMR investigations and solid state characterization of novel octafluorofluorene compounds

“…This discrepancy might be the effect of a hydrogen-bond involving the adjacent hydroxyl group in 4. However, an interaction FÁ Á ÁH-O, if present [12], is evidently not strong enough to prevent the fast rotation of the aryl ring at room temperature. The 19 F NMR spectrum of compound 5 (see Scheme 1) in THF-d 8 , exhibits three pairs of distinct resonances for the fluorines F2 0 and F2 00 , F3 0 and F3 00 , F4 0 and F4 00 , respectively.…”